The present invention relates to a dust suction apparatus, and more particularly relates to a dust suction apparatus for a semiconductor-manufacturing precision positioning table unit in a clean room.
A conventional dust suction apparatus for a positioning table unit in a clean room functions so that in order to remove powders produced by wear and minute particles of lubricant or the like (hereinafter referred to as dust) are produced from a moving part, such as a ball screw apparatus, a nut, a linear movement guiding mechanism and a support bearing, the dust and air located around the moving part are forcibly sucked together by a vacuum pump and sent to an air filter to catch the dust thereon and release the air to the atmosphere to keep no-dust environment therein as disclosed in the U.S. Pat. No. 4,955,244.
FIG. 4 shows the positioning table unit and the dust suction apparatus provided therefor. The unit includes a screw shaft 20, a motor 21, a support member 23, a linear guide 24, a nut 25, a base 31, and support blocks 32 and 33. The screw shaft 20 is supported at both the ends thereof by the support blocks 32 and 33 secured to the base 31 in the clean room 30, and is coupled to the motor 21 so that the shaft can be rotated by the motor. The linear guide 24 includes a bearing 24a and a rail 24b. The nut 25 is engaged with the screw shaft 20 and supported by the support member 23 and the linear guide 24 so that the nut can be straightly moved while being guided by the member and the guide. The nut 25 has a hole 22 extending from the outer surface of the nut to the inner surface thereof. The dust suction apparatus includes a spiral exhaust tube 26, a support means 26a, a suction pipe 26b, an dust suction pump 27, an air filter 28, a dust counter 34, and a control device 35. The spiral exhaust tube 26 is connected to the hole 22 of the nut 25 by a nipple, and supported by the support means 26a so that the tube can be elongated and compressed along the support means. The suction pipe 26a connects the exhaust pipe 26 to the dust suction pump 27. When the motor 21 of the table unit is put in action, the nut 25 is moved on the screw shaft 20 in a direction corresponding to that of the rotation of the motor. At that time, the dust generated at the nut 25 in the clean room 30 is sucked together with the air by the dust suction pump 27 through the exhaust tube 26 and the suction pipe 26b so that the dust is caught by the air filter 28, and the air is then returned to the clean room 30. An environmental servo system is composed of the dust counter 34 and the control device 35. The concentration of the dust in the clean room 30 is always monitored by the dust counter 34. Only when the concentration is lower that a prescribed level, the control device 35 acts to put the motor 21 in action.
Although the conventional dust suction apparatus which is of the vacuum suction type in which a dust generating part is subjected to vacuum suction to remove dust collects the dust effectively, the apparatus has problems that the exhaust tube 26 and the suction pipe 26b occupy spaces inside and outside the positioning table unit to restrict the travel of the table thereof, and the exhaust tube is moved along the movement of the table so as to make it likely to generate other dust.